1. Field of the Invention
This invention generally relates to a hydraulic torque transmitting device for transmitting torque via a fluid. More specifically, the present invention relates to a device that includes a fluid coupling or a torque converter.
2. Background Information
A torque converter is one type of hydraulic torque transmitting device that transmits power by means of a fluid inside a torus. A torus comprises three types of bladed wheel: an impeller, a turbine, and a stator. Some torque converters have a lockup device provided in the space between the front cover and the torus. The lockup device serves to mechanically transmit the torque of the front cover to the transmission side and is provided with a clutch mechanism and a damper mechanism. The clutch mechanism is designed so that it couples with or releases from the front cover in accordance with changes in the hydraulic pressure within the torque converter. The damper mechanism contains, for example, a plurality of torsion springs. When the lockup device is engaged, the torsion springs serve to absorb and attenuate torsional vibrations caused by such factors as fluctuations in the torque input from the engine.
In recent years, torque transmission using the fluid is only conducted during acceleration from a state of rest and the lockup device is engaged when the speed of the vehicle exceeds, for example 10 km. Regarding this kind of structure, wherein the lockup region has been expanded to the low speed region, there is a demand for improving the performance of the torsion springs so that fluctuations in the torque from the engine can be sufficiently absorbed and attenuated. More specifically, in order to obtain torsion springs having low stiffness, it is preferable for the coil diameter of the torsion springs to exceed a prescribed value. Meanwhile, the space where the torque converter will be disposed is clearly restricted in the axial direction and all components of the torque converter must fit there within.
In view of the above, there exists a need for a hydraulic torque transmitting device which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
One object of the present invention is to secure sufficient space in the axial direction for the damper in a hydraulic torque transmitting device that is provided with a lockup device having a damper.
The foregoing object is basically attained by providing a hydraulic torque transmitting device of the present invention that uses a fluid to transmit torque and is equipped with a front cover, an impeller, a turbine, and a lockup device. Torque is input to the front cover. The impeller and the front cover form a fluid working chamber. The turbine is disposed within the fluid working chamber so as to face the impeller. The lockup device is disposed between the front cover and the turbine. The lockup device has a clutch part for mechanically coupling said front cover to said turbine and a damper part for attenuating torsional vibration. In the vicinity of its outlet, the turbine has a linearly shaped part corresponding to the damper part.
With this hydraulic torque transmitting device, the linearly shaped part formed on the turbine makes it possible to distance the turbine from the damper part further in the axial direction than is possible with the prior art. As a result, the dimension of the damper part in the axial direction can be made larger. The linearly shaped part mentioned here refers to a straight line or a shape having a curvature that is nearly linear.
The hydraulic torque transmitting device in accordance with another aspect of the present invention is basically the same as prior aspect of the present invention with the additional stipulation that the linearly shaped part include a tapered surface that faces said damper part.
The hydraulic torque transmitting device the prior aspect of the present invention is basically the same as the prior aspect of the present invention with the additional stipulation that the tapered surface be formed by the turbine shell of the turbine.
The hydraulic torque transmitting device the prior aspect of the present invention is basically the same as any one of the prior aspects of the present invention with the additional stipulation that the ratio (S/D) of the length S of the tapered surface in the radial direction to the outer radius D of the torus be in the range of about 0.09 to about 0.19. With this hydraulic torque transmitting device, the linearly shaped part is established within a prescribed range. If the linearly shaped part is smaller than this range, it will not be possible to make the damper part sufficiently large in the axial direction. If the linearly shaped part is larger than this range, the turbine performance will decline.
The hydraulic torque transmitting device the prior aspect of the present invention is basically the same as any one of the prior aspects of the present invention with the additional stipulation that the flow passage area of the outlet of the turbine be smaller than the flow passage area of the inlet of said turbine. With this hydraulic torque transmitting device, the turbine outlet does not need to be closer than necessary to the stator even though a linearly shaped part is provided. As a result, a sufficiently large dimension in the axial direction can be secured for the stator in a torque converter that has a stator.
The hydraulic torque transmitting device the prior aspect of the present invention is basically the same as the prior aspect of the present invention with the additional stipulation that the flow passage area of the outlet of the turbine be smaller than the flow passage area of the inlet of the turbine by 2 to 5% of the flow passage area of the inlet of the turbine. With this hydraulic torque transmitting device, the flow passage area of the outlet of the turbine is smaller than the flow passage area of the inlet of the turbine by an amount that falls within a prescribed range. If the amount is larger than this range, the turbine performance will decline. If the amount is smaller than this range, then it will not be possible to secure a sufficiently large dimension for the stator in the axial direction in a torque converter that has a stator.
The hydraulic torque transmitting device the prior aspect of the present invention is basically the same as either of the two prior aspects of the present invention with the additional stipulation that the flow passage area of the outlet of the turbine be larger than the flow passage area of the inlet of the stator. With this hydraulic toque transmitting device, even though the flow passage area of the outlet of the turbine is smaller than the flow passage area of the inlet, the hydraulic torque transmitting performance does not decline because the flow passage area of the outlet of the turbine is larger than the flow passage area of the stator.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.